Floating-roof tank



y 1930. s. P. JOHNSON 1,758,225

FLOAT ING ROOF TANK Filed Dec 8, 1926 2 Sheets-Sheet l 10 10 /1f & 11

J 41 J I 4 X 11 22 /5 1- Patented May 13, 1930 UNITED STATES PATENTOFFICE SIDNEY P. JOHNSON, OF SAN FRANCISCO,

COMPANY OF CALIFORNIA, OF SAN FR DELAWARE FLOATING-ROOF TANK Applicationfiled December 8, 1926. Serial No. 153,302.

This invention relates to liquid storage tanks of the type which have aroof which floats upon the surface of the liquid in the tank; it iscustomary in such tanks to employ means for substantially preventing theevaporation of the liquidfrom the annular space between the tank walland the floating roof. The advantages of floating roofs for such tanksare well known, and one of the principal problems in their constructionis to provide an adequate seal for this annular space. It isimpracticable, by ordinary construction methods, to produce a roof thatwill operate efl'ectlvely where there is a very small clearance betweenthe floating roof and the tank, on account of irregularities which areincidental to the form of the tank wall. The evaporation loss from theannular space between such a floating roof and the tank wall Will beconsiderable unless some kind of expansible and contractible seal isused between the roof and the-tank. It is not necessary that this sealshall be absolutely gas-tight, however, as long as the liquid surfaceexposed is reduced to a small fraction of the whole area of the liquid.

The general object of this invention is to provide a seal for theannular space of such a tank which will operate without the formation ofexplosive gas and air pockets, at the same time providing means forsubstantially preventing, evaporation at this point, and providing formaintaining the roof centered in the tank, so that it is guided as theroof rises and falls with the liquid level.

Another object of the invention is to provide for sealing substantiallyall of the annular space Without necessitating the use of :1V flexiblediaphragm or apron such as is sometimes used to seal this space. Whilesuch diaphragms or aprons have some advantages, they are likely todeteriorate or soak up oil through their capillarity.

Another object of the invention is to provide means for mounting themovable members in such a way that their connections are pivotalconnections, thereby avoiding the excessive friction which would bedeveloped if mere sliding connections were used.

Further objects of the invention will appear hereinafter.

The invention consists of the novel parts and combination of parts to bedescribed hereinafter, all of which contribute to produce an eflicientfloating roof tank.

A preferred embodiment of the invention is described in the followingspecification, 'while the broad scope of the invention is pointed out inthe appended claims.

In the drawing:

Figure 1 is a plan of substantially onehalf of a floating roof tankembodying my invention.

Figure 2 is a vertical section through the tank, and particularlyillustrating the construction of the roof which enables it to preventthe formation of gas pockets under it.

Figure 3 is a vertical section taken through the edge of the roof andthe adjacent wall of the tank, upon an enlarged scale, certainpartsbeing broken away. This particularly illustrates the means for centeringthe roof and for sealing the liquid in the annular space between thefloating roof and the tank wall.

Figure 4 is a developed elevation, showin a short portion of the rim oredge of the roo and further illustrating details of the sealing means,certain parts being broken away.

In the drawing, 1 represents a tank of the usual cylindrical form, inwhich the liquid 2 is stored. On this liquid 11 floating roof 3 issupported, said roof consisting of a deck 4, which is substantiallycircular but preferably consists of a many sided polygon provided at itsedge with an upwardly extending flange 5. The deck 4 is constructed insuch a way that its central point 6 is slightly depressed, so that thedeck inclines upwardly slightly toward its edge. With this construction,any gas forming in the liquid naturall moves toward the edge of the roofand will not accumulate in pockets under it. In order to give the deckthis general form, I prefer to construct it of pyramidal form; that isto say, the deck is constructed in the form of an inverted pyramid, witha very large angle at the apex of the pyramid, which is disposed at thecentral point 6 of the roof. To this end, the deck 1s constructed of aplurality of substantially triangular sections or sectors 7. Thesesectors are constructed of flat form and are built up of plates rivetedtogether and at their inclined-side edges, they are connected togetherby angle-iron stiffeners 8 which are riveted to the abutting edges ofthe sectors.

In order to brace the roof and maintain it in its pyramidal form, Iprovide bracing on its upper side, said bracing comprising a centerstandard or short mast 9, from which di agonal tie-rods extend outwardlyto the edges of the roof. These tie-rods 10 'may extend directly overthe radial angle-irons 8 and they may he supported on intermediatestandards or stanchions 11 (see Figure 2). Their outer ends attach tothe parts 8.

The side edge or flange of the roof is disposed at sufficient distancefrom the wa l 12 of the tank to form an annular space 13. In order toseal this annular space; that is to say, to substantially cover theliquid. without the possibility of forming gas pockets at this point, Iprovide sealing means that extends under the edge of the roof andmaintains contact with the tank wall. This sealing means is constructedso that it substantially cc vers all of the area of the annular spacebut permits escape of vapors, thereby preventing the formation of gaspockets under it. For this purpose I prefer to provide a plurality ofshoes 14 corresponding to the sides of the polygon formed by the roof.These shoes have their side faces disposed slightly apart to permitindependent and free movement of the shoes and they are constructed sothat their inner edges 15 project under the edge of the roof (see Figure3). Each shoe swings on its support in a radial plane with respect tothe center of the tank. They maybe constructed of sheet metal and havesubstantially the form indicated; that is to say, they preferably have around or curved outer face or nose 16 curved in a vertical plane (seeFigure 3) which lies near or against the wall 12 of the tank.

Associated with the shoes 14, I prefer to provide means for maintainingthe roof 4 centered in the tank, and this means includes yielding meansfor holding the shoes in an outwardlyextending relation. "In order toaccomplish this, I mount the shoes so that they may rotate bodily in anare about a. substantially horizontal axis on the roof. In the pres--ent instance, I provide each shoe with a pair of arms 17 which extendupwardly, and which are mounted to rock on a pivot bar 18 supported onstanchions 19 which extend up from the deck a short distance inside ofthe flange or rim 5. The upper portions of these arms 17 aresubstantially hOIlZOIItiIL'bUt their outer portions have downwardlydisposed extensions '20 which are rigidly secured to the shoes. Theseshoes need not be buoyant and are preferably of sufficient weight tosubstantially overcome theirnatural buoyancy.

Associated with each pair of arms 17, I provide, means for yieldinglyurging the arms in a direction to hold the shoes substantially againstthe tank wall. For this purpose, I may provide the arms 17 with innerextensions 21 which carry adjustable weights 22, and the arms may alsobe provided with coiled springs 23, respectively, which exert an upwardthrust against the arms on the outer sides of the pivot rods 18, so asto assist the action of the weights 22. I prefer to construct the weightarms 21 in such a way that if the edge of the roof should approachunduly toward the tank wall at any particular point. then the lever armof the weight will increase so as to give the weight an increasedle"'erage in forcing the shoe out to its normal position. W'hile the useof weights, on account of this advantageous effect, is desirable, ifdesired. the weights can be omitted and the springs be used alone. Thesprings, however, cooperate with the weights when the weights are used.to make the arms more quickly responsive to changes in position of theroof, if it should get out of center.

The lower ends of the springs may be mounted in spring cups 24,respectively, which are supported on radial braces 25, in the form ofangle-irons, which connect the upper edge of the flange 5 with thestanchions 19. In order to enable the springs 23-to be adjusted, thelower ends are supported on spring seats 26, which may be forcedupwardly by an adjusting screw 27 which passes up through the horizontalflange of the angle brace 25.

If desired, the elevation of the pivot bar 18 may be made adjustable. Inorder to accomplish this, this pivot bar 18 may be supported on twoangle brackets 28 secured by a bolt. 29 passing through an adjustingslot 30 in the brackets.

In order to provide a close fit between the inner portion of each shoeand the edge of the roof, I construct the roof at its edge with a curvedface 31, the axis of curvature of which is at the axis of the bar 18.and the adjacent face 32 of the shoe 14 is similarly curved aboutthisaxis. In this way, as the shoes move in or out, they still maintaintheir faces quite close to the edge of the roof.

.The ends of the shoes 14 lie quite close together, as illustrated inFigure 1, so that while. they substantially close or cover the annularspace, they will permit an outward movement of any gas which forms underthe roof and which moves outwardly on its under side.

The curved face or plate 31 and theshoes 14 are located substantially atthe level of the liquid 2, which is indicated by the line 33. Thesefaces need not actually touch each other and hence they offer nofrictional resistance to the movement of the shoes. If desired,turn-buckles may be provided in the tie-rods 10.

The polygonal shape for the deck is preferable to a circular formbecause it is easier to fit the shoes 14 to a straight side. If thecircular form were used the upper face 32 of each shoe would have to becurved in two directions instead of merely of cylindrical form.

It is understood that the embodiment of the invention described hereinis only one of the many embodiments this invention may take, and I donot wish to be limited in the practice of the invention, nor in theclaims, to the particular embodiment set forth.

The slightly pyramidal form of the roof gives it a certain amount ofstiffness and eliminates the quality of limberness inherent in aperfectly flat roof floating on a liquid.

\Vhat I claim is:

1. In a sealing construction for liquids, the combination of a tank tocontain the liquid. a floating roof supported on the liquid so that anannular space is formed between the edge of the roof and the tank wall,a plurality of shoes having a support with a single pivotal axis on theroof, so as to swing bodily in an are about the pivotal support, andmeans for yieldingly pressing the shoes outwardly to hold their outerfaces adjacent the tank wall, said shoes being disposed with their endsspaced slightly apart so that they are independently movable andsubstantially seal the annular space between the roof and the tank wall.

2. In a sealing construction for liquids, the combination of a tank tocontain the liquid, a floating roof supported on the liquid so that anannular space is formed between the edge of the roof and the tank wall,a plurality of shoes haviiig pivotal supports on the roof with theirinner ends extending under the edge of the roof. the upper faces of saidinner ends and the adjacent edge of the roof being curved about the saidpivotal support as an axis, and means for yieldingly pressing the shoesoutwardly to hold their outer faces adjacent the tank wall.

3. In a sealing construction for liquids, the combination of a tank tocontain the liquid, a floating roof supported on the liquid so that anannular space is formed between the edge of the roof and the tank wall,a plurality of shoes substantially filling said annular space, armscorresponding tr each shoe and having a pivotal support on the roof,said shoes being disposed substantially at the liquid level with theirinner ends projecting under the edge of the roof, and means foryieldingly pressing the shoes outwardly to hold their outer facesadjacent the wall of the tank.

4. In a sealing construction for volatile liquids, the combination of atank to contain the liquid. a floating roof supported on the liquid sothat anannular space is formed between the edge of the roof and the tankwall, said roof having a substantially circular deck slightly dished sothat it is depressed at its middle point whereby gases forming under thedeck will move progressively toward said annular space, a plurality ofindependently movable shoes supported on the roof with their end facesdisposed slightly apart to permit their independent movement, lying onthe surface of the liquid, said shoes projecting out radially from theedge of the roof and substantially filling the said annular space, andmeans for yieldingly pressing the shoes outwardly toward the wall of thetank.

5. In a sealing construction for volatile liquids, the combination of atank to contain the liquid, a floating roof supported on the liquid sothat an annular space is formed between the edge of the roof and thetank wall, a plurality of shoes substantially sealing the space betweenthe roof and the tank wall and in contact with the liquid, a pluralityof arms carrying said shoes. pivotally supported on the roof andoperating to hold the inner ends of the shoes under the edge of theroof, and counterweights associated with the arms respectively, to forcethe shoes yieldingly toward the tank wall.

6. In a sealing construction for volatile liquids, the combination of atank to contain the liquid, a floating roof supported on the liquid sothat an annular space is formed between the edge of the roof and thetank wall, a plurality of shoes substantially sealing the space betweenthe roof and the tank wall and in contact with the liquid, a pluralityof arms carrying said shoes. pivotallv supported on the roof andoperating to hold the inner ends of the shoes under the edge of theroof, and a spring associated with the arms respectively, to force theshoes yieldingly toward the tank wall.

7. In a sealing construction for liquid the combination of a tank tocontain the liquid, a floating roof supported on the liquid so that asubstantially annular space is formed between the edge of the roof andthe tank wall. a plurality of shoes pivotally supported on the roof, andmeans for yieldingly pressing the shoes outwardly to hold their outerfaces adjacent the tank wall, said shoes capable of swinging bodily in aradial plane on the pivotal support so as to extend beneath the outeredge of the roof and being disposed adjacent each other so that theysubstantially fill the annular space between the roof and the tank wall.

8. In a sealing construction for liquid the combination of a tank tocontain the liquid,

a floating roof supported on the liquid so that an annular space isformed between the 7 edge of the roof and the tank wall, a plurality ofindependently movable shoes pivotally supported on the roof so as toswing in and out in a radial plane and substantially in contact with theedge of the roof, and means for yieldingly pressing the shoes outwardlyto hold their outer faces adjacent the tank wall. said shoes beingdisposed adjacent to each other and in contact with the liquid from theroof to the tanks wall so that they substantially seal the annular spacebetween the roof and the tank wall and operating to permit escape ofvapors between them and thereby prevent formation of a gas pocket underthe shoes.

9. In a sealing construction for volatile liquids the combination of atank to contain the liquid, a floating roof supported on the liquid sothat an annular space is formed between the edge of the roof and thetank wall, said roof having a substantially circular deck slightlydished so that it is depressed at its middle point whereby gases formingunder the deck will move progressively toward said annular space, aplurality of shoes supported on pivotal axes on the roof andsubstantially filling the said annular space, and means yieldinglypressing the shoes outwardly toward the wall of the tank, the said shoeshaving their upper faces curved about the said pivotal axes andprojecting under and substantially against the edge of the said roof.

10. In a sealing construction for liquids, the combination of a tank tocontain the liquid, a floating roof supported on the liquid so that anannular space is formed between the edge of the roof and the tank wall.a plurality of shoes substantially filling said annular space andpivotally supported on the roof with their inner ends extending underthe edge of the roof, the upper faces of said inner ends being curvedabout said pivotal support as an axis so as at all times to be in closejuxtaposition to the roof, and means for yieldingly pressing the shoesoutwardly to hold their outer faces adjacent the tank wall.

11. An oil tank having a floating roof of smaller diameter than thetank, sealing means interposed between the wall of the tank and thefloating roof lying on the surface of the liquid in the tank so as toengage the wall of the tank substantially at the liquid level andoperating to substantially cover the area of the liquid between the tankwall and the periphery of the floating roof, thereby preventing theformation of a space in which gas could accumulate, said meansconstructed so as to permit escape of gas and thereby preventaccumulation of gas pockets below the sealing means, and means forsupporting said sealing means on the floating roof.

12. An oil tank having a floating roof of smaller diameter than thetank, a plurality of sealin members interposed between the wall of t etank and the periphery of the floatin roof lying on the oil andsubstantially ing the annular space at the oil level between the tankwall and the periphery of the floating roof, said members constructed topermit escape of gas and thereby prevent accumulation of gas pocketsbelow the same, and means for attaching said members on the roof toenable the same to swing in a substantially radial plane with theirinner ends extending under the edge of the roof and substantially incontact therewith.

13. An oil tank having a floating roof of smaller diameter than thetank, a plurality of sealing members interposed between the wall of thetank and the periphery of the floating roof lying on the oil andsubstantially filling the annular space at the oil level between thetank wall and the periphery of the floating roof, said membersconstructed to permit escape of gas and thereby prevent accumulation ofgas pockets below the same, and means for attaching said members on theroof to enable the same to swing in a substantially radial plane withtheir inner ends extending under the edge of the roof and substantiallyin contact therewith, said members having noses at their outer endscurved in a vertical plane for engagement with the side wall of thetank.

14. An oil tank having a floating roof of smaller diameter than thetank, a plurality of sealing members interposed between the wall of thetank and the periphery of the floating roof lying on the oil andsubstantially filling the annular space at the oil level between thetank wall and the periphery of the floating roof, said membersconstructed to permit escape of gas and thereby prevent accumulation ofgas pockets below the same, and means for attaching said members on theroof to enable the same to swing in a substantially radial plane withtheir inner ends extending under the edge of the roof and substantiallyin contact therewith, said members having noses at their outer endscurved in a vertical plane for engagement with the side wall of thetank, and means for yieldingly holding the noses of the said sealingmembers against the tank wall.

15. In a sealing construction for volatile liquids, the combination of atank containing the liquid. a floating roof supported on the liquid sothat an annular space is formed between the edge of the roof and thetank wall, said roof comprising a substantially circular deck, aplurality of shoes lying at the surface of the liquid, means forpivotally supporting the shoes on the roof to swing under the roof attheir inner ends, with the upper faces of their inner ends lyingsubstantially parallel to the adjacent face of the roof.

Signed at San Francisco, California, this 19th day of November, 1926.

SIDNEY P. JOHNSON.

